This invention refers to a method for the combustion of liquid fuels in the gaseous state, and particularly of a method in which liquid fuel is evaporated by heat in a gasification chamber and the gasified fuel, after leaving the gasification chamber, is then burned with a controlled amount of air.
The U.S.-patent application Ser. No. 241,976, now U.S. Pat. No. 4,421,475, describes a burner in which liquid fuel is evaporated in the absence of air and then burned with a controlled amount of air. Evaporation takes place in a gasification chamber in which motor driven wiping means are provided to distribute the fuel and to prevent deposits on the walls. Preventing of deposits on the walls ensures proper gasification of the fuel. In operation pressurized fuel gas is generated which exits the gasification chamber through a nozzle and burns upon mixture with air supplied by a fan. Adjustable air control means, such as a flap, are provided to control the air supply. To obtain optimum efficiency the air supply should always be in an accurate relationship to the fuel supply. In other words, the stoichiometric relationship between air and fuel should be correct to provide for complete oxidation of the fuel. For this purpose a flap is set to correspond to a fixed burner capacity. This has the disadvantage that by a change of the viscosity of the liquid fuel more or less fuel is transported to the gasification chamber so that the burner will operate with a lack or an excess of oxygen. In either case efficiency is reduced, and in case of lack of oxygen the combustion gases have a high carbon monoxide and soot content, thus causing safety and environmental problems. Such problems may also occur when the burner is switched-off, because after standstill of the fan no air is supplied and the flame may continue to burn with an insufficient supply of oxygen as long as there is gaseous fuel under pressure in the gasification chamber, unless special means, such as a valve, are provided to prevent gasified fuel from leaving the gasification chamber after standstill.
Accordingly, an object of the embodiments of this invention is to provide a method which permits an automatic adjustment of the air supply in accordance with the amount of gasified fuel leaving the gasification chamber.
Another object of the embodiments of this invention is to provide a burner whose capacity can be altered during operation in accordance with the calorific requirements of the boiler or the like.
An advantage of the embodiments of this invention is the provision of a method and an apparatus which always provide for practically correct stoichiometric relationship between fuel and air over a wide range of burner capacities and independent from factors such as temperatures and viscosity of the liquid fuel, or a change in the rate with which the fuel pump pumps fuel into the gasification chamber. This provides for high efficiency and practically eliminates the generation of soot and carbon monoxide.
Another advantage of the embodiments of this invention is that the burner does not require additional valves for preventing gasified fuel from being burned after the burner motor is switched off.